Photoelectric sorting of small articles



Jul 28,1953

Patented July 28, 1953 PHOTOELECTRIC SORTIN G OF SMALL ARTICLES Herbert Frankel, London, England, assignor of one-half to R. W. Gunson' (Seeds) Limited,

- London, England Application June 7, 1949, Serial No. 97,652 In Great Britain June 16, 1948 This invention relates to apparatus for sorting small articles according to their different colours and/or light reflecting properties. For the sake of, simplicity it will be assumed in the following description that it is desired to sort light articles from dark articles 1. e. to separate those articles the surfaces of which reflect more light from those articles whose surfaces reflect less light, but it will be appreciated that this distinction is to be taken in itsbroadest sense since, by the use of suitable colour filters and/or selective colour-responsive devices, conditions may easily be established whereby the sorting of the light articles from the dark articles becomes, in fact, the separation of articles of one colour from articles of other colours. All that is necessary is to establish conditions in which those articles which it is desired to separate from the other articles mixed therewith have different light reflecting qualities.

In Patent No. 2,536,693 of record, there is described and claimed a, method of sorting small articles such as beans, peas and similar vegetable seeds the surfaces of which vary in their light reflecting properties which comprises selectively charging the articles electrically according to the amount, or kind, of light which they reflect and passing the charged articles through a steady electric field whereby they are selectively deflected according to their charge. Such a method of sorting mixed small articles will be hereinafter referred to, more particularly in the appended claim, as a method of sorting mixed small articles of the kind specified.

In the preferred method of separating small articles from their admixture with other small articles described in the said Patent No. 2,536,693 one set of articles is electrically charged and the other is not, and the charged and uncharged articles are passed-through a' steady electrostatic field whereby the charged articles are deflected and separated from the uncharged articles. 1

The chief object of the present inventionis to provide an improved method of charging those articles, such for example, as seeds, which are to be charged prior to their passage between the deflector plates employed to provide the steady electrostatic field.

According to the present invention, instead of being charged by reason of their contact with a charging electrode as in the arrangement described in Patent No. 2,536,693 mentioned above, the articles are charged by means of a corona discharge, preferably in mid-air.

1 Claim. (Cl. 209-111) 2 In order that this invention may be the more clearly understood and readily carried into eifect,

reference may be made to the accompanying articles, or of ensuring that they are selectively charged according to the amount, or kind, of light which they reflect is deemed to be unnecessary in the present application, since such details may be obtained from the specification of the Patent No. 2,536,693 above referred to. It may, however, be briefly stated and referring to the accompanying drawing that the mixed small articles to be sorted are fed from a feeding device it to a viewing area I I where they are illuminated by light from a lamp l2, light reflected from the article in question being picked up by one or more photoelectrical cells I3, the output from which is used to control the charge applied to the article.

'After passing the viewing and charging area ll, the articles fall between deflector plates I4 and i5 across which a high voltage electrostatic field is set up and then fall into receptacle [6 or receptacle l1 according to whether they have been charged or not.

In carrying out the present invention, instead of applying the charging potential obtained as a result of the response of the photoelectric cell [3 to the tip of a chute or groove down which the articles pass as was the case with the apparatus described in the Patent No. 2,536,693 above referred to, the chargingpotential is caused by setting up a corona discharge between a point I8 and an associated electrode IS, the article falling freely between the point and the electrode and being viewed by one or more photoelectric cells at a point just prior to its passing between the point and the electrode.

The viewing of the articles and the charging of the same, where necessary, thus takes place in mid-air and a more eificient and effective charging will be obtained. For example, charging the articles in mid-air by means of the corona discharge according to the present invention enables one to overcome the difficulty, sometimes experienced with the previous apparatus, of the "invention is not limited thereto. .forexample, to vary the degree of. charge. according to whether the article viewed by the charge on the article leaking away if the article were not the same shade or colour all over, and also prevents incorrect operation, as would be possible with the construction according to the above-mentioned Patent No. 2,536,693, if a second article of a different colour, 1. e. a light article instead of a dark article, moves into the viewing field before the first article left the contact electrode.

So far it has been assumed that in order to sort what may, for the sake of brevity, be termedthe good articles from the bad articles in a mixture of good and bad articles, one kind of articles, say the good articles, is-charged by the corona discharge whilst the bad articles are not charged, the responsefrom the photoelectric cells to the good articles initiating the discharge, whereas the response from a bad article does not initiate the diSchargeL'fJVJhilSt this is a very convenient method, the present It is possible,

photoelectric cells is good orbad. Separation will still. be effected as the articles pass between the deflector plates, since the amount by 'which an articleis deflected is a function of the acharge on the same.

In addition to the above mentioned advantages the" method of charging the articles according to .the .presentxinvention has the additional advantage that it enables a vastly increased range of articles to be sorted. One can, for example, sort objects which themselves are very bad conductors, oreven insulators, since the corona dis- I charge closely envelopes the articles and applies the charge, by reason of the ionised air, over the whole of the surface of the article at once. This :enablesthe: sorting of articles to be speeded up very considerably; since one of the limiting factors where theiartiole is charged by reason of its physical contact with a charging electrode is the time that it vtakesfor the charge to spread over thewhole surface of the article.

Furthermore; whilst a contact charging device necessarily covers at least'one side of the article from the illuminating light, acharging needle such as .is used to produce the corona discharge according to the. present invention is located away fromthe' article and leaves the Whole surface open to the light.

Itis convenient in. carrying out the present inventiontoernploy anioptical system adapted to illuminate the articles from practically all directions. Thus; for example, the light. source l2 may be arranged in a substantially enclosed, in-

ternally reflecting sphere iowith .comparatively small entrance and exit holes 2| and 22 for the articles} The apparatustmay also be'provided with open gaps 23.fordthe:.emission of light reflected by the'articles. in: combination with. illumination from the background. and photoelectrical cells I 3 to receive the. combinedilight coming from both the articles 'andethe background,- the re- -flected light from thebackground preferably being of such anintensity as to match the limit of reflectivity set for the articles to be accepted or rejected.

component in their velocity but fall substantially vertically.

-In an alternative method the articles to be sorted may be fed on to a pair of inclined conveyor: belts; the articles travelling along the contacting edges of the belts and being lined up to fall' off the endsv ofv the belts, one by one, in any suitable way. This method of feeding the articles isv particularly suitable where the articles are of small size.

:Any alternative method of feeding the articles, apparatus such as that used for packing tablets into bottles may be used, the. articles falling into a gripping point established between the peripheries of two contact rollers and thus being delivered from the gripping point to. the viewing and charging area one by one in a substantial vertical direction with a minimum lateral component in their velocity.

Iclaim I The method-of sorting small articles which vary intheir ability to reflect light in accordance with their individual light reflecting properties, which comprises selectively charging said articles electrically in accordance with their individual light reflecting properties bypassing said articles through a corona discharge from which said articles receive anelectrical charge depending on their light reflecting properties, and then deflecting said articles in proportion to the electrical charge carried byeach, thereby eiiecting a separation based on the individual light reflecting properties of saidsmall articles and wherein said small articles are illuminated, and are viewed by a-photoel'ectri'c cell as saidarticles are in mid-air,

"just prior to their entering said corona discharge, the response of said photoelectric cell to light re.-

flectedfrom each individual article determining whether saidarticle is charged by said corona discharge and, if so, the'amount of electrical charge placed thereon.

: HERBERT FRANKEL.

1:. :Beferences Cited. inzthe: file ofv this patent UNITED STATE-S PATENTS Number Name Date 888,432 Sutton May 19, 1908 1,120,560 Strong Dec. 8, 1914 1,386,287 Sutton Aug. 2, 1921 1,966,243 Hanna July 10, 1934 2,217,444 Hill Oct. 8, 1940 .-2,536,693 Okolicsanyi ..Ian..2,, 1951 FOREIGN PATENTS Number Country Date 492,035 Great Britain ,Sept. 14, 1930 

